Cooperative Binding of Substrates to Transketolase from Saccharomyces cerevisiae

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I. A. Sevostyanova¹, V. A. Selivanov², V. A. Yurshev³, O. N. Solovjeva¹, S. V. Zabrodskaya⁴, and G. A. Kochetov^1*

¹Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia; fax: (495) 939-3181; E-mail: kochetov@belozersky.msu.ru

²Barcelona University, Barcelona 08028, Spain

³Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, 119991 Moscow, Russia; fax: (495) 939-4195

⁴Institute of Biochemistry, National Academy of Sciences of Belarus, Bulvar Leninskogo Komsomola 50, 230017 Grodno, Belarus; fax: (0152) 43-4161

^* To whom correspondence should be addressed.

Received July 17, 2008; Revision received October 6, 2008

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Catalytic activity of two active sites of transketolase and their affinity towards the substrates (xylulose-5-phosphate and ribose-5-phosphate) has been studied in the presence of Ca²⁺ and Mg²⁺. In the presence of Ca²⁺, the active sites exhibit negative cooperativity in binding both xylulose-5-phosphate (donor substrate) and ribose-5-phosphate (acceptor substrate) and positive cooperativity in the catalytic transformation of the substrates. In the presence of Mg²⁺, nonequivalence of the active sites is not observed.

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KEY WORDS: transketolase, nonequivalence of active sites, bivalent cations, xylulose-5-phosphate, ribose-5-phosphate

DOI: 10.1134/S0006297909070128

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